Small pitch torch bump for mounting high-performance flip-chip

ABSTRACT

A new method and sequence is provided for the creation of solder bumps. The design of the invention implements a torch bump, which is a solder bump comprising a base over which a solder bump is created. A first layer of dry film is laminated over a supporting surface over which first a layer of UBM has been deposited. A base for the solder bump is created in a first opening created through the first layer of dry film, the created base aligns with an underlying contact pad. A second dry film is laminated over the surface of the first dry film, a second opening is created through the second dry film that aligns with the created base of the solder bump. The opening through the second dry film is filled with solder by solder printing, the first and second layers of dry film are removed, the deposited layer of UBM is etched. Reflow is applied to the deposited solder, creating the torch solder bump

BACKGROUND OF THE INVENTION

[0001] (1) Field of the Invention

[0002] The invention relates to the fabrication of integrated circuitdevices, and more particularly, to a method of creating a fine pitch,high-density solder bump.

[0003] (2) Description of the Prior Art

[0004] With continuously decreasing semiconductor device dimensions andincreasing device packaging densities, the packaging of semiconductordevice continues to gain increased importance. Metal interconnects,thereby including points of metal contact such as solder bumps, whichconnect semiconductor devices to surrounding circuits, have thereforebecome of relative more importance.

[0005] The increasing need for creating device interconnect traces ornetworks has led to the application of low resistance metals, such ascopper, for the interconnect traces while dielectrics having a lowdielectric constant or other interfacing layers such as air gaps orcavities are increasingly used in between signal lines. Another approachto solve problems of I/O interconnect capability has been to designchips and chip packaging methods that offer dependable methods ofincreased interconnecting of chips at a reasonable manufacturing cost.This has led to the development of Flip Chip Packages.

[0006] Flip-chip technology uses bumps (typically comprising Pb/Snsolders) formed over aluminum contact pads on the semiconductor devicesand interconnects the bumps directly to a packaging media, which areusually ceramic or plastic or organic material based. The flip-chip isbonded face down to the package medium through the shortest paths. Thesetechnologies can be applied not only to single-chip packaging, but alsoto higher levels of packaging, in which the packages are larger, and tomore sophisticated substrates that have multiple layers of interconnecttraces and that can accommodate several chips to form larger functionalunits.

[0007] The flip-chip technique, using an area I/O array, has theadvantage of achieving a high density of interconnect to the devicecombined with a very low inductance interconnection to the package. Thepackaging substrate is generally used for Ball Grid Array (BGA) packagesbut can also be used for Land Grid Array (LGA) and Pin Grid Array (PGA)packages.

[0008] The mounting of a flip chip over the surface of a printed circuitboard consists of attaching the flip chip to this board or to any othermatching substrate. A flip chip is a semiconductor chip that has apattern or array of terminals spaced around the active surface of theflip chip, the flip chip is mounted with the active surface of the flipchip facing the supporting substrate. Electrical connectors that areprovided on the active surface of the flip chip can consist of Ball GridArrays (BGA) devices and Pin Grid Arrays (PGA) devices. With the BGAdevice, an array of minute solder balls is disposed over the activesurface of the flip chip for attachment to the surface of a supportingsubstrate. For PGA devices, an array of small pins extends essentiallyperpendicularly from the active surface of the flip chip, such that thepins conform to a specific arrangement on a printed circuit board orother supporting substrate for attachment thereto. The flip chip isbonded to the printed circuit board by refluxing the solder balls orpins of the flip chip.

[0009] With the continuing decrease in the contact pads that are used toconnect pre-solder bumps thereto, the pitch of the solder bumps becomesincreasingly more important. The invention addresses this issue andprovides a method that significantly improves the pitch of the solderbumps that interface between a semiconductor device and the devicesupporting substrate over which the device is mounted.

SUMMARY OF THE INVENTION

[0010] A principle objective of the invention is to increase the pitchof an array of solder bumps.

[0011] Another objective of the invention is to create solder bumps fora high-density, high performance flip chip package.

[0012] Yet another objective of the invention is to create solder bumpsfor a high-density, high performance flip chip package usingconventional methods of semiconductor device processing.

[0013] A still further objective of the invention is to provide a highlyintegratable and manufacturable method of creating solder bumps for ahigh-density, high performance flip chip package

[0014] In accordance with the objectives of the invention a new methodand sequence is provided for the creation of solder bumps. The design ofthe invention implements a torch bump, which is a solder bump comprisinga base over which a solder bump is created. A first layer of dry film islaminated over a supporting surface over which first a layer of UBM hasbeen deposited. A base for the solder bump is created in a first openingcreated through the first layer of dry film, the created base alignswith an underlying contact pad. A second dry film is laminated over thesurface of the first dry film, a second opening is created through thesecond dry film that aligns with the created base of the solder bump.The opening through the second dry film is filled with solder by solderprinting, the first and second layers of dry film are removed, thedeposited layer of UBM is etched. Reflow is applied to the depositedsolder, creating the torch solder bump.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIGS. 1 and 2 shows cross sections of Prior Art solder bumps.

[0016]FIGS. 3 through 9 show the method of the invention for thecreation of a torch bump, as follows:

[0017]FIG. 3 shows the cross section or a semiconductor surface over thesurface of which a contact pad, a patterned and etched layer ofpassivation and a layer of UBM have been created.

[0018]FIG. 4 shows a cross section after a first mask of dry film hasbeen created.

[0019]FIG. 5 shows a cross section after the base for the torch bump hasbeen created.

[0020]FIG. 6 shows a cross section after a second mask of dry film hasbeen created, a layer of solder has been deposited.

[0021]FIG. 7 shows a cross-section after the first and second mask ofdry film have been removed.

[0022]FIG. 8 shows a cross section after the layer of UBM has beenetched.

[0023]FIG. 9 shows a cross section after the step of reflow of thedeposited solder.

[0024]FIGS. 10 through 12 show various dimensional configurations of thetorch bump of the invention.

[0025]FIG. 13 shows a cross section of two torch bumps of the inventioncreated side-by-side, dimensions are highlighted.

[0026]FIG. 14 shows a cross section of yet another creation of a torchbump.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] For reasons of comparison and improved understanding of theinvention, comparable conventional methods of creating a solder bump arefirst highlighted using FIGS. 1 and 2 for the purpose.

[0028] A conventional method that is used to create a solder bump over acontact pad is next highlighted. FIG. 1 shows an example of one of themethods that is used to create an interconnect bump. A semiconductorsurface 10 has been provided with a metal contact pad 12, thesemiconductor surface 10 is protected with a layer 14 of passivation. Anopening has been created through the layer 14 of passivation, exposingthe surface of the metal contact pad 12. Overlying layers 16, 18 and 20of metal are created by conventional methods of first depositing of alayer of dielectric (not shown) over the surface of the layer 14 ofpassivation for the creation of metal layer 16 and by selectivelycreating layers 10 and 20 over the surface of the created layer 16.Metal layer 16 is created by patterning and etching a deposited layer ofdielectric (not shown), creating an opening through the deposited layerof dielectric that aligns with the metal pad 14 and that partiallyexposes the surface of the metal pad 14. Layer 16 of metal is in contactwith the surface of the metal pad 14 inside opening created through thelayer 14 of passivation. A layer 18 of metal, typically usingUnder-Bump-Metallurgy (UBM), is created over the layer 16 of metal usingmethods of plating and the like. The region of layer 18 of metal that isabove the metal pad 14 will, at a later point in the processing, form apedestal over which the interconnect bump will be formed. This pedestalmay further be extended in a vertical direction by the deposition andpatterning of one or more additional layers, such as layer 20, FIG. 1.

[0029] A layer of photoresist (not shown) is deposited, patterned andetched, creating an opening that aligns with the contact pad 12 and hasa diameter about equal to the surface area of the upper surface of layer20. The opening created through the deposited layer of dielectric isfilled with solder, typically using methods of solder printing.

[0030] A solder paste or flux (not shown) is now applied to the layer 22of solder, the solder 22 is melted in a reflow surface typically under anitrogen atmosphere, creating the spherically shaped interconnect bump22 that is shown in FIG. 1.

[0031] The preferred materials for the various layers that are shown incross section in FIG. 1 are as follows:

[0032] For Layer 16 copper is the preferred metal

[0033] For Layer 18 nickel is the preferred metal, and

[0034] For Layer 20 gold is the preferred metal.

[0035] The selection of the materials that are used for the variousoverlying layers are determined by considerations of interlayeradhesion, metal diffusion, metal corrosion, issues of layer delaminationand the like.

[0036] increased device density brings with it increased closeness ofcomponents and elements such as solder bumps that are part of thecreated semiconductor device packages. This increased closeness isexpressed as a reduction in the spacing or “pitch” between solder bumpsof a semiconductor device package. State-of-the-art technology, usessolder bumps having a pitch of about 200 μm, which imposes a limitationon further increasing device density. The limitation in further reducingthe pitch of solder bumps is imposed by concerns of reliability, whichimpose a relatively large ball size for the solder bump. This relativelylarge solder ball restricts further reducing the solder ball pitch.

[0037] In the majority of applications, solder bumps are used asinterconnections between I/O bond pads and a substrate or printedcircuit board. Large solder balls bring with it high standoff since asolder ball with high standoff has better thermal performance (CTEmismatching is easier to avoid resulting in reduced thermal stress onthe solder balls). Large solder balls are therefore required in order tomaintain interconnect reliability. Low-alpha solder is applied to avoidsoft error (electrical or functional errors) from occurring, therebyeliminating the potential for inadvertent memory discharge and incorrectsetting of the voltage (1 or 0).

[0038] The cross section that is shown in FIG. 2 is essentially the sameas the cross section shown in FIG. 1 with the exception that in FIG. 2the solder 22′ overlies and covers the base layers 16, 18 and 20. Thisapplication reduces the potential exposure of for instance the copper oflayer 16 to the environment, thereby reducing the potential forcorrosion of the copper surface. The application that is shown in crosssection in FIG. 2 further improves solder bump 22′ reliability andreduces lamination exposure.

[0039] As previously highlighted, high-density, high-performancesemiconductor device packages require solder bumps of reduced bumppitch, increased bump height and reduced bump cross section.Conventional technology as highlighted above using FIGS. 1 and 2 arelimited in this respect by being limited in all three of the indicatedrequirements of bump creation. A number of technologies create overlyinglayers that form part of a solder bump by creating a photoresist maskusing a one-step photoresist exposure and development process. Thistypically requires a relatively thick layer of photoresist, whichintroduces design parameters of the created solder bump that arecontrary to the desired design parameters of solder bump pitch, crosssection and height.

[0040] The solder bumps that have been shown in cross section in FIGS. 1and 2 are created by first creating the patterned and developedphotoresist mask, then plating the layers 16 of copper, the layer 18 ofnickel and the layer 20 of gold. The photoresist mask is then removedafter which solder is applied over the surface of the created layer 20of gold using methods of solder stencil printing. This method howeverresults in a solder bump of considerable height and is limited inproviding soldier bumps of required cross section and required solderbump pitch. The invention provides a method that addresses theseconcerns.

[0041] The invention will now he described in detail using FIGS. 3through 9 for this purpose.

[0042] Referring first specifically to the cross section shown in FIG.3, there is shown a semiconductor surface 10, such as the surface of asubstrate, over which a contact pad 12 has been created. A patterned andetched layer 14 of passivation material is deposited over the surface oflayer 10, an opening (not highlighted) created through the layer 14 ofpassivation exposes the surface of the contact pad 12. A layer 24 ofUnder-Bump-Metallurgy (UBM), typically of Ti/Ni/Cu and of a thicknessbetween about 0.5 and 2 μm, is electroplated over the surface of thepatterned and etched layer 14 of passivation.

[0043] The cross section that is shown in FIG. 4 shows a patterned anddeveloped layer 26 of dry film. Layer 26 of dry film is laminated overthe surface of the layer 24 of UBM and then patterned and developedusing conventional methods of photolithographic exposure anddevelopment.

[0044] A layer of dry film conventionally comprises a photopolymer,which is an aqueous processable dry film resist that is designed foralkaline and acid etch applications and for pattern plating in copper,tin, tin/lead, Ni and Au. The chemical composition of a dry filmcomprises a multifunctional acrylic monomer.

[0045] The preferred dry film of the invention is of a negative typephoto-polymer. This results in surface areas of the layer of dry filmthat are exposed by G, H and I line UV light will remain over thesurface of the wafer while unexposed surface areas will be removed byapplying for instant an alkaline solution to the surface thereof.

[0046] The preferred thickness of the laminated layer 26 is betweenabout 70 and 150 μm but more preferably about 100 μm.

[0047] The inventions continues, FIG. 5, with the formation of the basefor the torch solder bump by electroplating the layers 28, 30 and 32,using the electroplating process. The preferred metals for the threeindicated and highlighted layers are as follows:

[0048] For Layer 28, copper is the preferred metal

[0049] For Layer 30, nickel is the preferred metal, and

[0050] For Layer 32, gold is the preferred metal.

[0051] As an alternate to the deposition of the three layers 28, 30 and32, the invention also provides for the deposition of a high-lead solderpaste over which eutectic solder paste is deposited. The high-leadsolder paste may be deposited instead of the layer 28 of copper afterwhich layers 30 (of nickel) and 32 (of gold) are deposited with thelayer of eutectic solder paste being deposited over the surface of theplated layer 32 of gold. For other applications, the layers 30 of nickeland 32 of gold may be omitted in which case the eutectic solder paste isdeposited directly over the surface of the deposited layer of high-leadsolder. For these applications, since the melting point of the high-leadsolder is higher than the melting point of the eutectic solder paste,only the deposited layer of eutectic solder paste will reflow duringsolder ball reflow.

[0052] In the cross section of FIG. 5, the highly reflective layer 32 ofgold is the upper layer which, due to its high degree of reflectivity,can be used as an alignment mark for the following exposure of a secondlaminated dry film layer. This lamination of a second dry film layer isshown in cross section in FIG. 6 after the second dry film layer 34 hasbeen patterned and developed again using conventional methods ofphotolithographic exposure and development. The opening that has beencreated through the second dry film layer 34 is aligned with the contactpad 12 and therefore with the plated layers 28, 30 and 32. The openingcreated through the second dry film layer 34 is filled with a layer 36of solder.

[0053] By now removing the layers 26 and 34 of dry film, the structurethat is shown in cross section in FIG. 7 is obtained. Using the createdtorch bump column 28/30/32/36 as a mask, the layer 24 of is UBM etched,the results of this etch have been highlighted in the cross section ofFIG. 8. Wet etching is the preferred method to etch the UBM layer 18.

[0054] The structure that is shown in cross section in FIG. 8 is readyfor solder reflow, creating the solder ball 36 that is shown in crosssection in FIG. 9.

[0055] To review the prior art process:

[0056] A semiconductor surface of provided, a contact pad having beenprovided over the semiconductor surface, a patterned and etched layer ofpassivation having been provided over the semiconductor surface,exposing the surface of the contact pad

[0057] A layer of UBM is electroless plated over the surface of thelayer of passivation including the opening created through the layer ofpassivation

[0058] A photomask is created over the layer of UBM, an opening createdthrough the photomask is aligned with the contact pad

[0059] Deposited are, in alignment with the opening created through thephotomask, layers of metal that form the base of the solder ball, suchas a layer of copper followed by a layer of nickel followed by a layerof gold after which and using the same photomask, a layer of solder isdeposited

[0060] The photomask is removed, and

[0061] Reflow is applied to the deposited layer solder.

[0062] To review and add to the invention:

[0063] The invention creates a torch bump, so called because the solderbump is created over and aligned with an underlying base layer formingin this manner a shape that resembles a torch

[0064] The torch bump comprises a base and a solder bump overlying thebase

[0065] The solder bump can be created having a diameter of about 100 μm

[0066] The base layer preferably comprises a first or lower layer ofcopper, created to a thickness of about 90 μm, a second or center layerof nickel, created to a thickness of about 5 μm and a third or upperlayer of gold, created to a thickness of about 5 μm

[0067] The torch bump of the invention is created using a two-layer dryfilm process

[0068] The lower or first layer of dry film is used for plating the baselayer of the torch bump

[0069] The base of the torch solder bump is used as the alignment markfor the patterning and development of the second layer of dry film

[0070] The upper or second layer of dry film is used for solder platingof the torch bump

[0071] The invention provides for creating the base of the torch bumpusing overlying layers of high-lead solder as a lower layer over which alayer of eutectic solder is pasted; layers of seed and barrier materialmay or may not be used in combination with these layers of high-leadsolder and the layer of eutectic solder

[0072] The creation of the torch bump comprises a two step platingprocess, a first plating process for the creation of the Cu/Ni/Au baseof the torch bump, a second plating process provides solder plating forthe solder bump

[0073] The invention provides for the creation of an ultra-fine pitchsolder bump

[0074] The height of the torch bump equals two times the height of a dryfilm mask

[0075] In comparing the invention with conventional methods of creatinga solder bump, whereby a one-time photolithographic masking and exposureprocess is used combined with a relatively thick layer of exposure mask,the advantage that is provided by the two-mask process of the inventionis that the invention solves problems of low-resolution caused by anultra-thick layer of dry film in addition to problems ofphotolithography alignment

[0076] By adjusting the ratio of opening height to opening diameter ofthe opening that is created through the second layer of dry film, thesize of the solder ball with respect to the size of the base of thetorch bump can be controlled, this is highlighted in FIGS. 10 through12, as follows

[0077] 1. FIG. 10 shows a cross section whereby the diameter 42 of thebase is larger than the largest diameter 46 of the solder ball which islarger than the diameter 44 of the contact surface between the solderball and the base of the torch bump

[0078] 2. FIG. 11 shows a cross section whereby the diameter 42 of thebase is equal to the largest diameter 40 of the solder ball which islarger than the diameter 38 of the contact surface between the solderball and the base of the torch bump, and

[0079] 3. FIG. 12 shows a cross section whereby the diameter 42 of thebase is smaller than the largest diameter 48 of the solder balls of thetorch bump.

[0080] The cross section that is shown in FIG. 13 is presented in orderto highlight dimensions of the torch bump where two torch bumps arecreated in adjacency to each other. The following parameters andstructural details are highlighted in the cross section of FIG. 13:

[0081]10, the surface of a substrate

[0082]12, bond pads created over the surface of substrate 10

[0083]14, a patterned and etched layer of passivation

[0084]50 and 52, equal to about 200 μm

[0085]54, equal to about 90 μm

[0086]56 and 62, equal to about 100 μm

[0087]57, two lines running through the center of the solder bumps 72 ina direction that is perpendicular to the plane of the substrate 10

[0088]56 and 60, equal to about 5 μm

[0089]64, a first dry film having a thickness of about 4 mil

[0090]66, a second dry film having a thickness of about 4 mil

[0091]68, a UBM layer

[0092]69, a copper base

[0093]70, a barrier layer preferably comprising nickel

[0094]71, a protective layer preferably comprising gold, and

[0095]72, a torch bump.

[0096]FIG. 14 shows yet one more application of the invention whereinare highlighted:

[0097]10, the surface of a substrate

[0098]12, bond pads created over the surface of substrate 10

[0099]14, a patterned and etched layer of passivation

[0100]73, a patterned and etched layer of UBM

[0101]74, the base of the torch bump, such as a layer of copper or alayer of high-lead solder

[0102]76, a non-solder wettable layer

[0103]78, a solder wettable layer, and

[0104]80, the solder bump of the torch bump.

[0105] Although the invention has been described and illustrated withreference to specific illustrative embodiments thereof, it is notintended that the invention be limited to those illustrativeembodiments. Those skilled in the art will recognize that variations andmodifications can be made without departing from the spirit of theinvention. It is therefore intended to include within the invention allsuch variations and modifications which fall within the scope of theappended claims and equivalents thereof.

What is claimed is:
 1. A method for the creation of a torch bump,comprising the steps of: providing a substrate, said substrate havingbeen provided with a contact pad over the surface thereof, a patternedand etched layer of passivation having been deposited over the surfaceof the substrate, exposing the surface of said contact pad, a layer ofUBM having been blanket deposited over the surface of the layer ofpassivation including the exposed surface of the contact pad; creating abase of said torch bump overlying said contact pad using a patterned anddeveloped first layer of dry film as a mask; creating a layer of solderof said torch bump overlying said base using a patterned and developedsecond layer of dry film as a mask; removing said patterned anddeveloped first and second layers of dry film, and applying reflow tosaid layer of solder.
 2. The method of claim 1, said creating a base ofsaid torch bump comprising the steps of: depositing a first layer of dryfilm over the surface of said layer of UBM; patterning and developingsaid first layer of dry film, creating an opening through said firstlayer of dry that aligns with said contact pad, creating a first mask ofdry film, exposing said layer of UBM; and depositing successive layersof metal over the exposed surface of said layer of UBM in accordancewith the opening created through said first mask of dry film.
 3. Themethod of claim 2, said successive layers of metal comprising: a firstlayer of copper deposited over the exposed surface of said layer of UBM;a second layer of nickel deposited over said first layer of copper; anda third layer of gold deposited over the surface of said second layer ofnickel.
 4. The method of claim 3, said first layer of copper beingdeposited to a thickness of about 90 μm.
 5. The method of claim 3, saidsecond layer of nickel being deposited to a thickness of about 5 μm. 6.The method of claim 3, said third layer of gold being deposited to athickness of about 5 μm.
 7. The method of claim 1, said creating a layerof solder comprising the steps of: depositing a second layer of dry filmover the surface of said first layer of dry film, thereby including thesurface of said base; patterning and developing said second layer of dryfilm, creating an opening through said second layer of dry that alignswith said base of said torch bump, creating a second mask of dry film,exposing said base of said torch bump; and depositing a layer of solderin accordance with the opening created through said second mask of dryfilm.
 8. The method of claim 2, said successive layers of metalcomprising: a first layer of solder deposited over the exposed surfaceof said layer of UBM; and a second layer of eutectic solder pastedeposited over said first layer of solder.
 9. The method of claim 8,whereby additionally a layer of nickel is deposited over the surface ofsaid first layer of solder after which a layer of gold is deposited overthe surface of said layer of nickel after which said second layer ofeutectic solder paste is deposited over the surface of said layer ofgold.
 10. The method of claim 1, said layer of UBM comprising nickel.11. The method of claim 10, said nickel being deposited to a thicknessbetween about 1 and 10 μm.
 12. The method of claim 1, with an additionalstep of etching said layer of UBM using said created base of said torchbump and said created layer of solder as a mask.
 13. The method of claim12, said etching said layer of UBM comprising a wet etch process. 14.The method of claim 1, parameters of first and second dry film thicknessin combination with parameters of said first layer of dry film as a maskand said second layer of dry film as a mask being selected such that thediameter of the base of said torch bump is larger than the largestdiameter of the solder ball of said torch bump which is larger than thediameter of the contact surface between the solder ball and the base ofthe torch bump.
 15. The method of claim 1, parameters of first andsecond dry film thickness in combination with parameters of said firstlayer of dry film as a mask and said second layer of dry film as a maskbeing selected such that the diameter of the base of the torch bump isequal to the largest diameter of the solder ball which is larger thanthe diameter of the contact surface between the solder ball and the baseof the torch bump.
 16. The method of claim 1, parameters of first andsecond dry film thickness in combination with parameters of said firstlayer of dry film as a mask and said second layer of dry film as a maskbeing selected such that the diameter of the base of the torch bump issmaller than the largest diameter of solder ball of the torch bump. 17.A method for the creation of a torch bump, comprising the steps of:providing a substrate, said substrate having been provided with acontact pad over the surface thereof, a patterned and etched layer ofpassivation having been deposited over the surface of the substrate,exposing the surface of said contact pad, a layer of UBM having beenblanket deposited over the surface of the layer of passivation includingthe exposed surface of the contact pad; depositing a first layer of dryfilm over the surface of said layer of UBM; patterning and etching saidfirst layer of dry film, creating an opening through said first layer ofdry film that aligns with said contact pad, thereby exposing the surfaceof said layer of UBM, creating a first mask of dry film; electroplatingat least one layer of metal over the exposed surface of said layer ofUBM; depositing a second layer of dry film over the surface of saidfirst layer of dry film; patterning and etching said second layer of dryfilm, creating an opening through said second layer of dry film thataligns with said contact pad, thereby exposing the surface of said atleast one layer of metal electroplated over the exposed surface of saidlayer of UBM, creating a second mask of dry film; depositing a layer ofsolder in said opening created through said second layer of dry film;removing said first mask and said second mask of dry film from thesurface of said layer of UBM; etching said layer of UBM using said atleast one layer of metal electroplated and said deposited layer ofsolder as a mask; and applying reflow to said deposited layer of solder.18. The method of claim 17, said electroplating at least one layer ofmetal comprising: a first layer of copper deposited over the exposedsurface of said layer of UBM; a second layer of nickel deposited oversaid first layer of copper; and a third layer of gold deposited over thesurface of said second layer of nickel.
 19. The method of claim 18, saidfirst layer of copper being deposited to a thickness of about 90 μm. 20.The method of claim 18, said second layer of nickel being deposited to athickness of about 5 μm.
 21. The method of claim 18, said third layer ofgold being deposited to a thickness of about 5 μm.
 22. The method ofclaim 17, said electroplating at least one layer of metal comprising: afirst layer of solder deposited over the exposed surface of said layerof UBM; and a second layer of eutectic solder paste deposited over saidfirst layer of solder.
 23. The method of claim 22, whereby additionallya layer of nickel is deposited over the surface of said first layer ofsolder after which a layer of gold is deposited over the surface of saidlayer of nickel after which said second layer of eutectic solder pasteis deposited over the surface of said layer of gold.
 24. The method ofclaim 17, said layer of UBM comprising nickel.
 25. The method of claim24, said nickel being deposited to a thickness between about 1 and 10μm.
 26. The method of claim 17, said etching said layer of UBMcomprising a wet etch process.
 27. The method of claim 17, parameters offirst and second dry film thickness in combination with parameters ofsaid first layer of dry film as a mask and said second layer of dry filmas a mask being selected such that the diameter of the base of saidtorch bump is larger than the largest diameter of the solder ball ofsaid torch bump which is larger than the diameter of the contact surfacebetween the solder ball and the base of the torch bump.
 28. The methodof claim 17, parameters of first and second dry film thickness incombination with parameters of said first layer of dry film as a maskand said second layer of dry film as a mask being selected such that thediameter of the base of the torch bump is equal to the largest diameterof the solder ball which is larger than the diameter of the contactsurface between the solder ball and the base of the torch bump.
 29. Themethod of claim 17, parameters of first and second dry film thickness incombination with parameters of said first layer of dry film as a maskand said second layer of dry film as a mask being selected such that thediameter of the base of the torch bump is smaller than the largestdiameter of solder ball of the torch bump.
 30. A structure for a torchbump, comprising: a substrate, said substrate having been provided witha contact pad over the surface thereof, a patterned and etched layer ofpassivation having been deposited over the surface of the substrate,exposing the surface of said contact pad, a layer of UBM having beenblanket deposited over the surface of the layer of passivation includingthe exposed surface of the contact pad; a base of said torch bump havingbeen created overlying said contact pad using a patterned and developedfirst layer of dry film as a mask; a layer of solder of said torch bumphaving been created overlying said base using a patterned and developedsecond layer of dry film as a mask; said patterned and developed firstand second layers of dry film having been removed; and reflow havingbeen applied to said layer of solder.
 31. The structure of claim 30,said base of said torch bump having been created comprising: a firstlayer of dry film having been deposited over the surface of said layerof UBM; said first layer of dry film having been patterned anddeveloped, having created an opening through said first layer of drythat aligns with said contact pad, having created a first mask of dryfilm, exposing said layer of UBM; and successive layers of metal havingbeen deposited over the exposed surface of said layer of UBM inaccordance with the opening created through said first mask of dry film.32. The structure of claim 31, said successive layers of metalcomprising: a first layer of copper having been deposited over theexposed surface of said layer of UBM; a second layer of nickel havingbeen deposited over said first layer of copper; and a third layer ofgold having been deposited over the surface of said second layer ofnickel.
 33. The structure of claim 32, said first layer of copper havingbeen deposited to a thickness of about 90 μm.
 34. The structure of claim32, said second layer of nickel being deposited to a thickness of about5 μm.
 35. The structure of claim 32, said third layer of gold havingbeen deposited to a thickness of about 5 μm.
 36. The structure of claim30, said layer of solder having been created by: a second layer of dryfilm having been deposited over the surface of said first layer of dryfilm, thereby including the surface of said base; said second layer ofdry film having been patterned and developed, having created an openingthrough said second layer of dry that aligns with said base of saidtorch bump, having created a second mask of dry film, having exposedsaid base of said torch bump; and a layer of solder having beendeveloped in accordance with the opening created through said secondmask of dry film.
 37. The structure of claim 31, said successive layersof metal comprising: a first layer of solder having been deposited overthe exposed surface of said layer of UBM; and a second layer of eutecticsolder paste having been deposited over said first layer of solder. 38.The structure of claim 37, whereby additionally a layer of nickel havingbeen deposited over the surface of said first layer of solder afterwhich a layer of gold having been deposited over the surface of saidlayer of nickel after which said second layer of eutectic solder pastehaving been deposited over the surface of said layer of gold.
 39. Thestructure of claim 30, said layer of UBM comprising nickel.
 40. Thestructure of claim 39, said nickel having been deposited to a thicknessbetween about 1 and 10 μm.
 41. The structure of claim 30, additionallysaid layer of UBM having been etched using said created base of saidtorch bump and said created layer of solder as a mask.
 42. The structureof claim 41, said etching said layer of UBM comprising a wet etchprocess.
 43. The structure of claim 30, parameters of first and seconddry film thickness in combination with parameters of said first layer ofdry film as a mask and said second layer of dry film as a mask havingbeen selected such that the diameter of the base of said torch bump islarger than the largest diameter of the solder ball of said torch bumpwhich is larger than the diameter of the contact surface between thesolder ball and the base of the torch bump.
 44. The structure of claim30, parameters of first and second dry film thickness in combinationwith parameters of said first layer of dry film as a mask and saidsecond layer of dry film as a mask having been selected such that thediameter of the base of the torch bump is equal to the largest diameterof the solder ball which is larger than the diameter of the contactsurface between the solder ball and the base of the torch bump.
 45. Thestructure of claim 30, parameters of first and second dry film thicknessin combination with parameters of said first layer of dry film as a maskand said second layer of dry film as a mask having been selected suchthat the diameter of the base of the torch bump is smaller than thelargest diameter of solder ball of the torch bump.